This investigation concerns three biologically important issues: 1) dynamical aspects of protein structure, 2) the stereochemical details of protein folding, and 3) the packing of solvent molecules at the protein-solvent interface. The conclusive resolution of these issues depends on the ability to assign the individual hydrogen atom positions in a protein. Neutron diffraction, due to its unique capability to locate directly hydrogen (or deuterium) atoms, is a technique particularly well suited to answer these questions. Neutron diffraction studies will be performed on two protein systems: 1) trypsin and 2) crambin. Crambin, due to its high diffractability (.8Angstrom), can be studied at virtually atomic resolution and, therefore, act as an ideal model system to assess a number of basic stereochemical parameters (planarity of peptide bonds, H-bond geometry, torsional bond perturbations, etc.) which dictate the folding patterns of proteins. A unique approach to study conformational dynamics is proposed by coupling the hydrogen exchange technique to neutron diffraction. This will allow for direct quantification of exchange at specific sites which when combined with the information of the groups location in the 3-D structure will provide details of the nature and extent of short-lived conformation fluctuations which are inherent features in all protein systems. A density model of the solvent envelope surrounding the protein surface will be determined experimentally to measure its average character and local systematic variations with respect to its distance from the interface and the chemical properties of neighboring protein groups. This will be done by analyzing H2O - D2O difference maps, a procedure unique to the neutron diffraction method.